This report deals with the water resource and its exploitation from an engineering point of view, but is aimed at an essentially non-engineering audience. Any state-of-the-art report is bound to be incomplete and, in this case, the sins of omission have to be weighed against the inclusion of material, based on practical experience, of the kind which cannot be found in textbooks.
This report is, therefore, a personal perspective of the authors, who have had to be selective in covering a very wide field in a very small volume. It has been necessary to concentrate, as far as possible, on principles, giving details only in order to enable the reader to pursue a particular topic through the references cited in the text. One of the major aims of the report has been to give an insight, for non-specialists in this field, into the wide range of problems in water development and to provide general guidelines for future planning.
The report begins with a description of the major controls on the climatic environment. The variation of rainfall in time and space is presented as the central problem of water development. It attempts to explain why there is often too little rainfall or too much, and why the situation changes from year to year, with the greatest variability occurring in the areas of greatest need. It highlights the problems of predicting this variability and of describing it in a way which can be used for planning purposes.
Chapter 3 deals with what happens to rainfall after it reaches the ground. It describes the various components of the hydrological cycle and how they are interrelated. There is also a brief discussion of how the components can be measured or estimated and how the hydrological cycle can be affected by man's activities.
Chapter 4 considers the potential water resources of the pastoral areas of tropical Africa. The various types of water resource are classified as a prelude to discussing the means of exploitation in Chapter 6.
Chapter 5 is a brief introduction to the problems of water quality. This is frequently a constraint on water development activities and it is therefore appropriate to emphasise water quality considerations as a prelude to exploitation.
Chapter 6 covers a very wide field, of necessity in a general and skeletal manner. The means of exploitation of a water resource are site specific, and the range of options depends as much on economic considerations as on technical feasibility. An attempt has been made to introduce the important concepts of appropriate technology and community participation. Emphasis has been placed on low-cost systems, on the assumption that more elaborate and sophisticated projects are dealt with in detailed feasibility studies by professional water engineers and scientists, who are able to present and evaluate the full range of options for a particular project.
The final chapter deals with some aspects of planning which are related specifically to the evaluation of water resources. Two vital aspects operation and maintenance - are also discussed, to emphasise the need for simple and reliable water supply systems. These should involve the local communities, as far as possible, in every stage of planning, implementation and operation.
In conclusion, some recommendations are made on key areas which play an important role in the successful implementation and continued operation of schemes for water supply. A plea is made for the diversion of some funds into practically orientated research, if only to keep pace with the need for new solutions to problems in the development of water resources in the face of rapidly increasing populations.
It is often said that the amount of rainfall is not the problem; it is the distribution of that rain fall, in space and time, which forms the basis of the dilemma for planners. It is of no help to subsistence pastoralists to know that nearby humid areas have plentiful water if the costs of distributing that water far outweigh the economic returns. It is technically feasible to pump water from lakes and distribute it by pipelines to almost any pastoral area. Saline water can be desalinated and rivers impounded to provide supplementary water supplies. These methods, however, are extremely high-cost solutions to the problem and cannot be justified by even the most generous cost-benefit analysis.
Low-cost solutions have to be sought for the foreseeable future, until energy costs form a much smaller proportion of the operating costs of water supply schemes. In the meantime, the arid and semiarid pastoral regions of tropical Africa will be faced with making the best use of their available water resources. This precludes the large-scale transfer of water from the wetter regions or from large perennial rivers. It implies that the exploitation of water resources must be based on three maxims:
- conservation
- optimum utilisation
- efficient management.
The first of these, conservation, implies not only the storage from wet season to dry season of whatever rain falls, but also the retention of that rainfall on the surface to allow maximum infiltration. To this end, it necessitates soil conservation and the arresting of vegetational degradation caused by overgrazing, burning or deforestation. The point is made in Chapter 6 that investment in water supply schemes will largely be futile without the management of river catchments or areas of groundwater recharge. The corollary is that investment in soil and water conservation makes sound economic sense, in view of the high cost of providing water supplies, rectifying damage to roads and hydraulic structures, and removing sediment from irrigation channels.
Optimum utilisation involves knowing what the options for the exploitation of water resources are, and selecting the 'best' option in terms of a specific criterion. This criterion needs not necessarily be that of low cost where the social benefits are unquantifiable. It is difficult to assess the benefits of improved health and of the increase in time available for other occupations which arise from the provision of safe and adequate water supplies. It is suggested that planning of water supplies is best accomplished within a complete drainage basin or region. What might appear the best option at project level may not be the best one in the context of national planning or of large multipurpose schemes. Adequate surveys are an essential prerequisite for optimum utilisation For such surveys, a quantitative knowledge of the components of the hydrological cycle is required, together with the predictive tools to assess what is feasible for the future.
Efficient management requires no explanation other than to emphasise that it includes the establishment of efficient operation and maintenance procedures. Wherever possible, these procedures should be based on the expertise of local communities, with a minimum of reliance on outside assistance. Imparting a sense of ownership of the water supply scheme to the local community is essential to its long-term operation.
No attempt has been made to give cost indicators for the various options proposed, except in relative terms. It was thought that giving examples of cost would be of little relevance to future projects. Costs are critically sensitive to the location of project areas, both in terms of access to sites and in relation to the prevailing technological capacity of the country in question.
Another consideration is that many countries are busily engaged in developing low-cost technologies to enable them to move towards the target of providing safe drinking water within easy reach of rural populations. These activities have been stimulated by the United Nations 'International Drinking Water Supply and Sanitation (IDWSS) Decade' (1980-1990). Dramatic reductions in per caput cost have already been reported from Malawi (UNDP/Malawi Government, 1982) in relation to new low-cost boreholes and dug wells. A recent seminar on low-cost groundwater development for rural communities, held in Malawi in December 1982, also indicated that similar cost reductions are being achieved in Sudan, Benin, Upper Volta and Togo.
While the value of the United Nations 'decade' activities in focusing attention on the plight of the developing countries must be acknowledged, it is clear that this drive has been initiated during the worst possible period for obtaining the necessary funds to achieve its designated targets. The world economic recession, and an increasing detachment by traditional donor agencies from their commitment to developing countries, has meant that funds are available for only a fraction of the proposed activities. At the same time, the World Bank estimates that there are 1.2 billion rural people (excluding those in China) who still lack access to safe water (World Bank, 1982). The same report shows that out of the total investments by the International Development Association of US$ 6610 million between 1961 and 1982, less than 4% was on water supply. It is encouraging to note, however, that two thirds of that 4% have been invested since 1978 - a reflection of the World Bank's increasing focus on water and sanitation.
Concentrating on human populations does not divert funds away from providing water for livestock. On the contrary, the spin-off from the IDWSS decade is likely to be very beneficial to the livestock populations and their owners. There are indications that investment in the water sector in African countries may double, but this will be due to a redirection of funds into water and sanitation projects rather than an increased total commitment from donors (World Water, 1982). If this is the case, every effort should be made to increase the cost effectiveness and success rate of water projects. In this way water development can assist in increasing the survival rate of livestock in drought years, in raising the standard of living of pastoralists, and in improving the quality of life of those people living in the arid and semiarid areas of tropical Africa.
